We propose to adapt a high-resolution ECG system (PELEX) that includes the features of programmable <V resolution ECG data acquisition, wireless communication, near real-time advanced analysis algorithms, and provider notification to identify age- and gender-specific ECG patterns in normal infants and in infants with congenital heart disease (CHD) before and after cardiac surgery (PELEX-C). Abnormal cardiac electrical activity in infants and children is associated with cardiac failure following heart surgery and is an important cause of prolonged hospitalization and sudden death. (1-28) Despite a "successful" operation, the risk for cardiac decompensation and death in infants with CHD persists following hospital discharge and has been associated with post-operative arrhythmias. The risk for sudden death can be as high as 16% for infants with Hypoplastic Left Heart Syndrome following the palliative Norwood procedure. Recent studies have applied high-resolution (<V) electrocardiogram (ECG) analysis techniques to detect myocardial ischemia and injury in children with CHD.(19,24-28) In addition to the "usual" ECG parameters of heart rate (HR), cardiac time intervals (PR, QRS, QTC,), and changes in the position of ST segments, high- resolution ECG analysis can detect a broad range of clinically relevant <V variations in cardiac waveforms that represent increased risk for arrhythmia and death in adults but comparable studies have not been done in children. Thus, there is a clinical need to rapidly detect abnormal ECG patterns in pediatric patients and an opportunity to use the features of a PELEX system to identify subtle, sub-threshold pro-arrhythmic ECG patterns associated with cardiac injury/ischemia.(29-37)Medical intervention can then optimize patient outcomes by treating patients at risk for developing life-threatening arrhythmias prior to clinical decompensation. SPECIFIC AIM 1. Adapt the PELEX acquisition and analysis algorithms (e.g. normative values of heart rate, QRS and T wave axis, depolarization, repolarization, temporal instability, arrhythmia) to the age and gender-specific parameters and patterns of infants and children (PELEX-C). SPECIFIC AIM 2. Use PELEX-C to acquire and analyze cardiac electrical patterns in a prospective, cross-sectional cohort of healthy infants (n = 40). SPECIFIC AIM 3. Use PELEX-C to acquire and analyze normal and abnormal cardiac electrical activity in a prospective, cross-sectional cohort of infants with congenital heart disease undergoing cardiac surgery including cardiopulmonary bypass in the first 90 days of life (n = 20). The PELEX-C system represents an age-specific extension of the FDA-cleared, high-resolution, wireless, personal ECG system (PELEX) to a unique sub-population of at-risk infants and children. A much larger market is anticipated for monitoring changes in cardiac electrical activity in children with non-cardiac diseases such as chronic lung diseases, cancer, and neurologic disorders.(38, 38b-e). [unreadable] PUBLIC HEALTH RELEVANCE: We propose to identify unique patterns of abnormal cardiac electrical activity after congenital heart surgery using high-resolution recording and multi-dimensional analysis so that we can identify post- operative patients at risk for cardiac arrhythmia and clinical deterioration. Medical care can then be intensified for these high-risk infants in order to prevent post-operative arrhythmias, prolonged hospitalization, higher morbidity and hospital costs, and sudden death. Identifying "at-risk" patterns of cardiac electrical activity using high-resolution analysis (of patterns now considered normal using standard analysis) may also be very important in identifying patients with non-cardiac diseases who are at increased risk for arrhythmia due to treatment with drugs that directly or indirectly impact cardiac electrical and mechanical performance. [unreadable] [unreadable] [unreadable]